1. Field of the Invention
This invention relates to evaporative coolers and more particularly to an improved automatic flushing and draining apparatus for use with evaporative coolers.
2. Description of the Prior Art
All evaporative coolers of the type having an air handler mounted in the cabinet for drawing air into the cooler through wettable cooler pads and delivering the evaporatively cooled air to a point of use, have the necessary water supply contained within a floor pan or sump. The water level within the sump is maintained at a predetermined level by a float controlled inlet valve that is suitably connected to a source of water under pressure, such as a municipal water line.
The most common type of evaporative cooler in use today employs a pump which is mounted in the sump of the cooler and operates to supply water to the cooler's water distribution system, which in turn distributes the water to the top of the cooler pads. The water trickles down through the cooler pads and the air being drawn therethrough by the air handler is cooled by the well known evaporative principle, and the unevaporated water drains, under the influence of gravity, from the pads back into the sump.
Another type of evaporative cooler which, although is not as common as the above described type, is gaining commercial acceptance, and will hereinafter be referred to as a pumpless cooler for reasons which will become apparent as this description progresses. In this pumpless type cooler, each of the pads of the cooler are of endless belt-like configuration and are carried on a pair of vertically spaced horizontally extending rollers, one of which is rotatably driven by a suitable electric motor, so that the pad is continuously moving over the rollers. The lowermost rollers of each pair of rollers are located in the cooler's sump so that the pads will be continuously driven through the water contained in the sump and are thus kept in a wetted state.
During operation of either of the above described pump-type or pumpless type evaporative coolers, the water, which inherently contains minerals, such as sodium and calcium chlorides and other impurities, will increase as to its concentration of those minerals due to the evaporation process. As the mineral concentration increases, the rate of precipitation will also increase which results in mineral deposits, or scaling, of the various cooler components. Such mineral deposition causes calcification of the cooler pads, clogging of the water passages, corrosion of the metal and the like, but the most serious problem is with the electric motors and wiring. When the mineral salts, which are electrovalent compounds, are deposited on the wiring terminals, and the various parts of the electric motors themselves, they attack those components and cause premature failures. Further, those compounds are hygroscopic in nature and will thus attract moisture out of the atmosphere even when the evaporative cooler is inoperative, and thus, salt induced deterioration is a continuing process. To keep such mineral deposits to a minimum, the cooler should be periodically drained, flushed, and refilled with fresh water. However, since such draining, flushing and refilling is something which should be accomplished on a regular and a rather frequent schedule, as determined by the characteristics of the water, it is something that is almost always forgotten, or simply ignored.
The above described problems of mineral deposition is compounded by the fact that the water is stored within the sump which serves as a reservoir. Thus, the various cooler components are exposed to a relatively large body of water in the bottom of its cabinet. Unless the sump is drained at the end of a cooling season, or prior to other periods of nonuse, such direct exposure of the components to the water body is something that can, and often is, continuous whether the cooler is operating or not.
The above described problems and shortcomings of prior art evaporative coolers is something that has long been recognized and various attempts have been made to solve, or at least, minimize some of those problems. For example, devices which dispense chemicals into the water to reduce mineral concentration and deposition problems have been suggested, however, such devices have not received widespread commercial acceptance due to the minimal and sometimes questionable benefits derived, cost, and the maintenance requirements.
In addition to the mineral build-up problem, other contaminants will collect in the water supply of evaporative coolers due to the air washing effect which results from drawing air through the wet cooler pads. Airborne pollen, dust, and the like, will be washed out of the ambient air as it passes through the cooler pads into the cooler, and those contaminants will be carried by the water back into the cooler's operating water supply. Those contaminants are detrimental to cooler life and efficient cooler operation, and, of course, a major concern relating to such airborne contaminants is bacteria. Airborne bacteria, which is washed from the incoming air into the cooler's water supply, and bacteria from other sources, is responsible for musty, or fishy odors coming from the cooler and delivered to the point of use by the air coming from the cooler. Further, such bacteria is responsible for fungi, algae and other thallophyta growths, which can, and very often occur in evaporative coolers.
One particular prior art device has been suggested in U.S. Pat. No. 2,828,761, for automatically draining, flushing, and replacing the water in the sump of a pump-type evaporative cooler and for draining a large portion of the water therefrom when the inlet water supply to the sump is shut off. Briefly, this prior art device includes a sheet metal dam which is located within the sump of the cooler. A oneway check valve is located in the wall of the dam so that water is free to flow from the main reservoir portion of the sump into the relatively smaller dam portion but is prevented from flowing in a reverse direction. A pump and siphon valve are located inside the dam and a float controlled water inlet valve is located in the main reservoir portion of the sump to maintain the water level in the sump and in the dam, due to the free flow through the checking valve, at a predetermined level. During operation of the cooler, the pump delivers water from within the dam portion to the cooler's water distribution system which in turn supplies water to the cooler pads, and the unevaporated water will return from the pads, by gravity, to the main reservoir portion of the sump. When the pump is turned off, water in the cooler's water distribution system will drain back into the dam area only, due to the reverse flow checking provided by the check valve, thus raising the water level therein to a point where it primes the siphon valve. When the siphon valve is so primed, water in the dam will be drained therefrom and the water in the main reservoir portion of the sump will flow through the check valve into the dam and will exit the dam through the siphon valve. When the water supply is left on during such an operation, the result is that a draining, flushing and water replacement action takes place, and due to the outlet and siphon drain valve being sized to drain the sump at a faster rate than the water inlet line can replace the water, the water level will drop until the siphon valve looses its prime, whereupon refilling of the sump with fresh water takes place under control of the float operated inlet valve. This same operation occurring when the water supply to the cooler is shut off results in draining of most of the water from the sump.
This particular prior art flushing and draining device has not received commercial acceptance for several reasons. In the first place, the amount of water contained in the water distribution plumbing system of an evaporative cooler is quite small and will, in many cases, be insufficient to achieve priming of the siphon valve. Secondly, the check valve of this prior art structure is a constant source of problems, in that the water pressure differential on the opposite sides thereof is all that can be relied upon for opening and closing of the valve, and that pressure differential is exceedingly small. The small pressure differential relied upon to open and close the check valve precludes the use of a spring or other device to bias the valve towards its closed position. Therefore, the check valve is a passive rather than a positively acting device, and achieving a fully closed position when such a state is critical is oftentimes not achieved. To illustrate this point, there can be no leakage through the check valve when the draining cycle is initiated, in that such leakage would prevent the water level in the dam from reaching the point where the siphon valve is primed. In addition to the passive action of the check valve, it by necessity, is operated under water and this subjects the valve to corrosion, mineral scaling, and the like, and the valve is often jammed by foreign matter such as dirt, wood shavings from the excelsior pads, and the like. Thirdly, this prior art device is incapable of completely draining all of the water from the dam and the main reservoir portion of the sump, in that both the check valve and the inlet to the siphon valve are spaced upwardly from the bottom of the sump. Therefore, the desirability of draining the sump when the cooler is inoperative cannot be completely achieved.
Therefore, a need exists for a new and improved automatic flushing and draining apparatus for evaporative coolers which overcomes some of the problems and shortcomings of the prior art.